1. Field of the Invention
This invention relates to new derivatives of styryl-like compounds with improved stability which undergo color change, coloration or bleaching reversibly or, in some cases, irreversibly in response to external activating energies such as light, heat, ions, electric potential, pressure, radiant rays and so on.
2. Description of the Prior Art
Styryl-like compounds which show a coloring or bleaching or color-changing behavior on application, for example, of electric potential are disclosed in U.S. Pat. No. 4,003,633. These compounds are of the general formula (I) ##STR3## in which Q represents a benzene ring with or without substituents and/or condensed ring(s), R.sub.1 and R.sub.2 may be the same or different and represent lower an alkyl radical, a hydroxyalkyl radical or an alkoxyalkyl radical, R.sub.3 represents hydrogen, an alkyl radical, a halogen, a nitrile radical, an aromatic radical or a phenoxy radical, Y represents O or S, Z represents an alkylene radical or2 to 4 carbon atoms with or without alkyl substituent(s), necessary to form a ring structure together with ##STR4## and A represents a condensation reaction residue of an aromatic aldehyde, a heterocyclic aldehyde, an aromatic nitroso compound or heterocyclic nitroso compound.
When external energies are applied to these styryl-like compounds, the chemical structure of the compound is changed reversibly from one to another state, thereby showing color. However, repeated application of external energies shows a tendency that the compounds are deteriorated in quality and are not completely bleached when the external energies have been removed.